The goal of this research is to understand the functional organization of the vertebrate retina. Methods which examine quantitatively the physiological properties of individual neurons as well as their patterns of connections will be used. The physiological properties of individual retinal neuorns will be established by using white-noise stimuli either in the form of light applied to the photoreceptor system or by injection of white-noise current into individual neurons and recording responses from synaptically coupled close-by neurons. The structural organization will be established by labeling these physiologically identified neurons with horseradish peroxidase (HRP) and examining the over all structure of these neurons in the light microscope and their synaptic connections in the electron microscope. We plan to combine with this approach the labeling of presynaptic terminals with radioactive neurotransmitter candidtates in order to determine the polarity of the synaptic input onto the HRP injected neurons. Finally, by analyzing voltage transients following brief current pulses and by making appropriate anatomical measurements of labelled cells we plan to examine the cable properties of retinal neurons. The physiological and morphological techniques will be applied to the catfish retina and also to the tadpole and adult bullfrog retina in order to determine the progressive changes in information processing in a developing vertebrate retina. Our long term goal is to establish the principles of information processing which will enable the construction of a general model of the vertebrate retina.